Level



Dec. 1, 1953 I I I J. ROTHSTEIN LEVEL Filed Sept. 19, 1950 INVENTOR Jerome ATTORNEY Patented Dec. 1, I953 :oiFiE lcE 1 ZTClims.

'l The t invention described "herein, f n patented, "may be'manufacture'd andnsed. by orforkthe LGovernment for governmentali'purposes, Without thefpayment tct'me otanywoyalty thereon.

"Thisinvention relates to'an improvementdn "spirit levels. More particularly, the-inventionis concerned with bubble levels of the spirit *level type. for determining truehorizontal.

Conventionalspirit levels having an air-bubble under which afliquidccntain'ed 'irra tiibe'moves to show angular displacement are Well known in the art, 'However, in the placement'of:pre ci si'on instruments these levelsoo' not satisfactorily determine.extremelvsmall tilts from thehorizontal with" any degree of'fine "sensitivity.

Accordingly, it "is aniobject oiithisinvention to provide an improvedhubble type'spirit level" for "determining truehorizontal.

Another object of the inventionfis'toprovide'a bubble spirit level" ofhighi'precisicn"fondetermim .ing small anglesof tilt'tvith' ahigh' degree of sensitivity.

A further. object of this inventionisi to? provide a spirit level lcontaining "aniindic'ator "birbble pushed between balancedliquid'bodies to measure true horizontal: slight. deviations fronr'true horizontal with mechanical precision.

Other objects and advantages 'will-be apparent from the following description With'r'eference' to the accompanying. drawings, wherein:

Figure 1' is a side 'vi'ewiin"pai'tiar'crossaseetion of the spirit level embd iyingmy invention;

Figure 2 is a modification of Figure Yshowing the indicator level tubein a raised positiomto-preventbubble loss; 7

Figure 3 is a'modification' of Figure'z andillustrates the application of a'siphon to equalize liquid "volumes in the spirit level;

i"Figure 4 is a side 'Vl8W' in partial cross section illustrating a 'closed'moiiification of'FignTeB and "Figure 5 is a n'lt'udification Of Figtl1e 4 i11HStT9it ing. a convexed capillary"in the spirit *level.

"Figure 1 illustrates the"generalstructural'plan and underlying" principles of -'improvement spirit levels, a transparent "capillary tube 40 of unit length L anclhaving a cross-sectional bore area," for example; of 1 mm. *is provided -at its open ends Withvertical 'tiibes 'If)!" containers i l ancl i 2 each" having a cross' section'al bdretatrea, 'for example, of 3;3"cm. hereinafter? designated as area (a) and area (A). respectively. The capillary tube it is small enough so' that thecap'illary "effect produced 'th'ereby will cause 'the' biibble -to "completely fill the crosssectional area of th tube,

" effectively separating the 'liqui cl an the tnhefiso ..2 thativhen the' t'iibe'is" tilted'th liquid cannot-flow around the bubble, butohly push it along. Since =-"the-bore' of 'thecapillary' tube "I in is much smaller 't'han the bores of 'the containers i l and I 2 when :6 the" level.=is tiltd from the horizontal, and the *liqnid" in' ithe containers 1 I and 'i 2 seeks "a common level; the resulting movement of theindicat- 'ing' biibblein the capillary tube termin -he greatly -magilified, and the device willlthereforel accu- 10 rately' indicate 'very minute'i'deviationsifrom"the horizontal. "The tube 'ifi inay; if 'desiredfbeprovidedw-ith a set'of: scale markings '3 i3 and i3 wvhichzmaybe" calibrated on thefibasisiofidistance l or angular displacementuofa an airlhuhble i 4, or -15 a; similarfotherrequivalent indicator. 'lhe'bubrile i iltisliinstalled in the: capillary: tube? 1 i3 'by-"xbeing "Ltrapped?thereinlbyaany conventionalimethodcand showneascpositionedz between; two equal volumes of water; or. other:equivalentiiliquid eontaineolcin -=2051the capillary: tube :l flrandscontainers: i i. and? l 2. .r'iAs lclearlyishowniinittheadrawings, the :levelzr-of i'thelliquidtwithin'the containers 1 l andsi 2 :is "conrtsiclenablma'bove the pointsfof :eonnectionr ofthe I capillar 'y;or i1'1dic'ating'tubewith thecontainers. -35 As' illustrated, -theairtlcuicble I 4 is'positionedat lithe? midpoint :'01';Izero.i;marking iof leveling; capil lary tubeJlllfiWhenithe two liquid volumes ,int'the containers l l and? i'Z'Fare.:balanced onxa horizon- .1321 izlevel. .Upon 2 tilting not: the tube 1 H3 and; its tassociatedicontainers I [and t2 the liquid-volumes Linreetch":"containereare displacedandin seeking :a new-level; commensurate with the angle of :clis- .iplacement. pushv'thez' air. bubble to the right 01' 1=left,::dependentnupon the: angle: oftilt.

,-.It'-"Will be apparent that an open-ended struc- :ture as shown by'l iigurel' l 'is subject. to the loss -of-the:- bubb1e-l hen the-tube it is til-tecirat a sufficientanglet-to permittha fluid from one 'nenctcontainer topushtheibubbleninto, theother nend container. flmsu'chabubbleloss may. beavoided agpermanent itypellev'elloithe character here- -.inldescribed I by; providingffor example, ."closure membersor sealed; ends on. containers H and, as illustrated."in? Figure 4. For example, with liquict'volumesiin each of the containers 1 l' and I 2' which may be"dis'placd or *moved' from-container' to container in an amount almo'stbut not quite -'equa1' to 'thevolume of liquid contained" in the capillary Hi, the bubble M cannotbe forced en the way through i the -capillary level tube. --Othervvise, forexample, =as-shown by the balance we thefigures the and containers 5 i and l2 -may he joined-at their base' portions' by- -a capillary ii 6i inverted U shape having ncwnturnea vertical ess seeticnsofi legs w and l'i formed frame-portion of the capillary tube I which are in effect extensions of the capillary bore in capillary tube I5, Figure 2. These downturned legs I6 and H are joined to the bases of containers SI and I2 and form vertical capillary lifts or extended capillary passageways which prevent the loss of bubble Id upon greater angular tilt than can be made by structure heretofore described. In this form the short length of the legs it and H, with respect to sensitivity of measurement, is negligible and the length L is a measure of the distance indicated in the Figure 2.

With reference to Figure 3, the downturneo capillary sections it Ii are illustrated as being provided with enlargements or traps I6 and I! in the capillary bore next to the junctures of tube 5 with the liquid containers I! and I2. These enlarged bore portions 56' and ii of capillary tube I5 provide a clearance space which prevents loss of the bubble I l from the capillary by permitting passage or flow of liquid thereunder when the level is tilted excessively.

In order to provide for a setting of the bubble It and to equalize the amount of liquid on both sides of the bubble i a siphon tube I3, Figure 3,

may be utilized. To illustrate, the siphon tube is is filled with water or other liquid contained in the level and dipped into the containers H and it. To cut off the siphon flow, the downturned ends of the tube It may be removably mounted within receptacles or sleeves I9 and 28 in containers ii and 12 respectively. These receptacles or sleeves i9 and 26 are ground to receive the tube ends making fluid -tight joints, and while the tube ends are inserted within the sleeves i9 and 29, the tube 18 is closed off from communication with the liquid in the containers i I and I2. If desired, only one end may be fitted for closure. To reset the bubble the ends of tube It are withdrawn from the sleeves i2 and 2t, and the bubble is set as if the device were a conventional spirit level. Further, the ground fittings 29 and/or 253 may be disposed of and the siphon flow controlled by the inclusion of a suitable valve and stopcock it. Because of the siphon action liquid levels in the Wide bores in containers ii and I2 will be equalized.

To illustrate a permanent type liquid leveling and bubble setting arrangement, there is shown in Figure 4 a secondary tube is connecting the bases of containers II and i2 through which fluid flow is controlled by suitable valve and stopcock 2t. When the bubble I6 is set at zero or midpoint of the capillary tube 5 5 the stopcock is closed and the indicating bubble becomes highly sensitive to any angular displacement of the level. The usual care should be observed relative to liquid contamination with respect to valve lubrication. As illustrated by Figure l, the-ends of the large bore of containers 5 I and 12 are closed or sealed with covers I I and I2 respectively and the level operates in the manner as described for the other figures which may likewise be covered, sealed or closed when the devices are utilized as permanent spirit levels. !8 of Figure 3 when utilized with a valve and stopcock I 8' can be sealed through covers I i and 52' as shown in Figure 4.

A further modification for preventing bubble loss is shown in Figure 5, wherein the capillary tube i5 is curved with the convexed side up, as illustrated, and in addition is provided with the auxiliary enlargements It and il in the lower ends of capillary tube IE5 to function in the man:

If desired, the siphon" ner as described. In addition to providing a. sensitive leveling structure the convex curvature of capillary tube I5 forms an arc which may carry a scale from which a tilt angle can be read. With the bubble set and valve and stopcock 20 open an angular position may be determined by the movement of bubble I 4 under the scales 2! and 2|. Thereafter, with valve and stopcock 2t closed. the level becomes extremely sensitive to slight and small changes in angles of tilt. This level and the other levels as described may be independently utilized or otherwise provided with precision mountings having Vernier and micrometer scales or mirrors to get routine sensitive horizontal and angular measurements with an accuracy comparable to interferometric methods, and obtains such measurements in a much simpler manner.

In the structures as above described, any liquid of suitable viscosity and non-corrosive to the capillary may be used. Such liquids, for example, may be in the nature of mercury, alcohol, water and numerous oils. As described, the structures may be open or closed, and when open, liquids of high volatility would be of disadvantage from the standpoint of vaporization under conditions of use. In any event. with the liquids as described, an air bubble or other suitable indicator bubble does not stick or allow for passage of liquid thereunder in the narrow portion of the capillary tube. The bubble moves with the liquid a distance proportional to the ratio of the cross sectional area A of the vertical tube to the cross sectional area A of the capillary tube.

In place of an air bubble, any suitable indicating medium may be employed. For example, the bubble which is merely an indicator may be replaced by the boundary between two immiscible liquids such as oil and Water, kerosene and alcohol, mercury and alcohol, or any other combination of such liquids. One or both of the liquids would be colored to present a clear line of demarcation between the liquids. Alternatively, a droplet of mercury or a metal ball could replace the bubble. Where a heavy indicator such as mercury droplet or metal ball is used, the U-structure of Figures 2, 3, 4, and 5 would be inverted, as the heavier indicator would seek the lowest point. Wherever the term bubble is used in the specification and claims, it is intended to cover all such Well-known bubble equivalents.

Having thus described my invention what I claim is:

1. A unitary hand-manipulated portable level comprising a pair of spaced upstanding containers of relatively large cross sectional area and free from connection with a base or supporting surface, an elongated small bore capillary tube extending generally horizontally between the containers and connected with the sides of the containers a substantial distance below their tops, said capillary tube having an indicating scale marked thereon for coaction with a movable bub ble disposed Within the capillary tube and completely filling the cross sectional area thereof. the bubble serving to completely separate two masses of a liquid held by the capillary tube and containers on opposite sides of the bubble, the liquid serving to propel the bubble through the capillary tube when the level is tilted from the horizontal, the capillary tube having portions of enlarged cross sectional area near its ends and near its junctions with the containers, said portions forming traps to prevent the bubble from leaving the capillary tube and entering either 5 container, a substantially horizontal by-pass tube connecting the lower ends of the containers below the capillary tube, and a stopcock connected in the by-pass tube.

2. A unitary hand-manipulated portable level 5 comprising a pair of spaced upstanding containers of relatively large cross sectional area and free from connection with a base or supporting surface, an elongated small bore capillary tube extending generally horizontally between the containers and connected with the sides of the containers a substantial distance below their tops, said capillary tube having an indicating scale thereon for coaction with a movable bubble disposed within the capillary tube and completely filling the cross sectional area thereof, the bubble serving to completely separate two masses of a liquid held by the capillary tube and containers on opposite sides of the bubble, the liquid serving to propel the bubble through the capillary tube when the level is tilted from the horizontal, a substantially horizontal by-pass tube connecting the lower ends of the containers below the capillary tube, and a stopcock connected in the bypass tube.

JEROME ROTHSTEIN.

6 References Cited in the file of this patent UNITED STATES PATENTS Number Number Name Date Hicks et al Aug. 16, 1898 Cable June 19, 1900 Upson July 23, 1935 Gardner Jan. 3, 1939 Gardner et 'al. Feb. 13, 1940 Young May 30, 1950 Dahm Nov. 11, 1952 FOREIGN PATENTS Country Date France Jan. 11, 1904 Great Britain of 1907 Germany Apr. 27,1915 England May 7, 1931 Germany of 1930 France of 1936 Great Britain of 1937 Germany of 1938 

